The present invention relates to a lamp for motor vehicles constructed by joining a front lens and a lamp body, and to a s method for producing such a lamp.
Many vehicular lamps are constructed by joining a front lens and a lamp body. Conventional joining methods having included indirect joining in which the joining is done via a seal member and direct joining in which the joining is done by abutting the front lens directly to the lamp body. As a specific method for indirect joining, hot melt sealing or the like is well known, and as a specific method for direct joining, heating plate welding, vibration welding, and ultrasonic welding are well known.
For indirect joining, additional costs are incurred for the is sealing member, and a relatively large groove needs to be formed for applying the sealing member. Further, the need arises for a decorative treatment to make the sealing member in the groove difficult to see from the outside of the lamp.
Direct joining can solve the aforementioned problems arising from the presence of the sealing member. However, conventional direct joining has problems as will now be explained.
Heating plate welding generates protruding weld portions, so-called xe2x80x9cfoam burrsxe2x80x9d, on both sides of the joint interface, which degrades the outward appearance of the lamp. Vibration welding also generates relatively large burrs on both sides of the joint interface, thereby again degrading the appearance of the lamp. Further, in ultrasonic welding, in areas where the shape of the joint interface of the front lens and the lamp body changes three dimensionally and the curvature thereof becomes large, joining becomes impossible or difficult such that a problem arises in that sufficient joint strength cannot be obtained.
In view of the foregoing problems, the present invention has been made.
It is an object of the present invention to provide a vehicular lamp constructed by joining a front lens and a lamp body having an improved appearance around the joint interface and sufficient joint strength, even in regions where the shape of the joint interface changes three-dimensionally.
The present invention achieves the aforementioned and other objects by providing an improved structure for the joint portion of the front lens and the lamp body, and a joining method employing the same.
That is, the present invention provides a vehicular lamp in which the front lens and the lamp body are joined together, wherein a sealing leg is formed on the front lens and a receiving face against which a tip face of the sealing leg abuts is formed on the lamp body, and a tip face of the sealing leg and the receiving face are joined by laser welding.
The aforementioned xe2x80x9claser weldingxe2x80x9d means a joining method whereby a laser beam penetrable member and a laser beam impenetrable member are welded together by heating the laser beam impenetrable member by irradiating a laser beam on the abutting face of both members through the laser beam penetrable member in a state where the laser beam penetrable member which can be penetrated by a laser beam is abutted against the laser beam impenetrable member. The type of laser used for such laser welding is not particularly limited. For example, a semiconductor laser, a YAG laser or the like can be used.
The material for the aforementioned lamp body is not particularly limited as long as the material cannot be penetrated by a laser beam but instead heats up and melts upon irradiation by a laser beam. It is preferable to enhance the laser beam absorption ability of the lamp body as much as possible by adding an auxiliary material such as carbon black in order to perform more efficient laser welding.
The materials for the aforementioned front lens are not particularly limited as long as they can be penetrated by visible light and a laser beam and can be fixed to said lamp body by the melting thereof.
As illustrated in the aforementioned structure, in the vehicular lamp according to the present invention, a sealing leg is formed on the front lens and a receiving face to which the tip face of the sealing leg extends is formed on the lamp body, and the tip face of the sealing leg and the receiving face are joined by laser welding. The following effects thereby can be obtained.
Employing laser welding enables joining without generating large burrs or the like on the sides of the joint interface. Also, by employing laser welding, even in regions where the shape of the joint interface of the front lens and the lamp body changes three-dimensionally, because the laser beam only reaches the joint interface the joining operation can be carried out without difficulty, thereby ensuring a sufficient joint strength.
In addition, in accordance with the present invention, because the abutting portion of the tip face of the sealing leg and the receiving face defines the joint interface, the laser beam can be irradiated to the abutting portion from the front side of the front lens through the sealing leg. Therefore, even if the laser beam enters from a diagonal direction to some extent relative to the front lens, it is reflected internally by both side faces of the sealing leg and is able to reliably reach the tip face of the sealing leg such that the lamp body is able to be efficiently heated without reduction of the energy of the laser beam.
Therefore, in a lamp in which the front lens and the lamp body are joined according to the present invention, the appearance quality around the joint interface is improved and sufficient joint strength is ensured, even if the shape of the joint interface changes three-dimensionally.
In the aforementioned structure, by forming both side faces of the sealing leg in a tapered shape, part of the laser beam that has entered the front lens is able to reach the tip face of the sealing leg an increase in energy density by internally reflecting (i.e., totally reflecting) off both side faces of the sealing leg. Accordingly, the lamp body can be heated with even greater efficiency. In addition, forming of both side faces of the sealing leg in a tapered shape allows the base end portion of the sealing leg to be made wider, even if the tip face of the sealing leg is small, which facilitates irradiation of the laser beam into the sealing leg.
In this case, a xe2x80x9ctapered shapexe2x80x9d means that both side faces of the sealing leg narrow from the base end portion toward the tip face of the sealing leg at an angle (for instance, approximately 2 to 6xc2x0) that is greater to some extent than a draft angle (usually approximately 1.5xc2x0) employed when molding the front lens.
Also in the aforementioned structure, providing a positioning groove in the receiving face of the lamp body for preventing displacement of the sealing leg allows the laser welding to be performed while the front lens and the lamp body is are maintained in a predetermined physical relationship. Further, even if some burrs are generated due to laser welding, the burrs can be confined to the positioning groove, thereby providing a superior appearance quality around the joint interface. The positioning groove does not need to be as large as the groove needed for applying a seal member as required in the aforementioned indirect joining technique, thus eliminating the risk of degrading the appearance quality around the joint interface due to the presence of the positioning groove.
Further in accordance with the invention, employing a front lens in which the tip face of the sealing leg thereof is formed so as to have a convex lens shape allows, during laser welding, the laser beam which has penetrated the sealing leg and reached the tip face thereof to be emitted toward the receiving face as a focused beam, thereby enabling even more efficient heating of the lamp body.